It is known to dry cylindrical objects and in particular tubular cores for paper rolls, in drying plants, by arranging the moist tubes in rows and columns and to introduce the tube formation into a special drying plant or drying chamber which is ventilated with hot air.
The tubes are dried very slowly and are held in the drying chamber for a very long time, so that no distortion will occur in the tubes, such as curving of the tubes along their longitudinal axes or deviation from a true circle in cross-section.
It is also known with such drying plants to take measures which will ensure that respective tubes are maintained in their given order of formation.
It can be mentioned that the lengths of tubes which are used as cores for paper rolls normally vary from between 1 and 12 meters.
Various high frequency dryers are known to the art for different specific fields and technical applications. An example of such dryers is described and illustrated in U.S. Pat. No. 3,329,796. Reference is also made to the apparatus described and illustrated in U.S. Pat. No. 2,597,923.